The present invention is directed towards an apparatus for dispensing the contents of a plurality of pre-loaded syringes. More particularly, the present invention is directed towards an apparatus for injecting the fluid contents of a plurality of pre-loaded syringes into the receiving port of a gas chromatograph.
Most prior art devices for automatically injecting fluid samples into the receiving port of a gas chromatograph utilize a single syringe in conjection with a plurality of sample containers. In a typical apparatus, a single syringe is inserted into a sample container and the fluid sample therein is drawn into the syringe barrel. The syringe needle is then removed from the sample container and inserted into the receiving port of a gas chromatograph. The plunger of the syringe is then depressed and the fluid contents injected into the chromatograph for analysis.
After the sample has been injected, the syringe needle is withdrawn from the chromatograph and the syringe is flushed with a solvent to prevent contamination of the next sample. The syringe needle is then inserted into a second sample container and the procedure is repeated. The requirement that the syringe be flushed with solvent between each sample injection in the prior art devices has necessitated the utilization of expensive pumps and associated pneumatic controls.
The present invention eliminates the needs for expensive equipment by utilizing a plurality of pre-loaded syringes and a simple electro-mechanical device for injecting the fluid contents of each syringe into a chromatography column. More particularly, in accordance with the present invention a plurality of pre-loaded syringes are placed on a rotary wheel or similar mechanism which intermittently positions each syringe coaxial with the injection port of the chromatograph. As each syringe is brought into alignment with the injection port, a drive arm advances the syringe needle into the injection port and depresses the syringe plunger so as to inject the sample into the chromatography column.
In order to keep the samples in the syringes, prior to the insertion of the syringe needle into the receiving chamber of the chromatograph, the tip of the syringe needle is capped with a coating of a plastic substance such as Tygon (Trademark). During the injection process, the syringe needle penetrates the Tygon coating at the same time as it breaches the outer surface of the septum of the injection port of the chromatograph. After the sample has been injected into the chromatography column, the syringe is withdrawn from the injection port and returned to the rotary wheel and a new pre-loaded syringe is positioned coaxial with the injecting port of the chromatograph.
While the present invention is utilized primarily in conjunction with a gas chromatograph, it may also be utilized with other appropriate sample testing devices.
For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.